Cross-direction elasticized composite material and method of making it

ABSTRACT

A cross-directional elasticized composite includes a facing layer and a plurality of elastic filaments disposed in the cross direction. A method for making the cross-direction elasticized composite by continuously disposing molten elastic filaments on the facing layer and in the cross direction, is also provided.

BACKGROUND OF THE INVENTION

Laminates having elasticity in the cross-direction have previously beenprepared by bonding a neck-stretched (“necked”) nonwoven web, such as aspunbond web, typically formed of inelastic filaments, to an elasticfilm or nonwoven web. These laminates, referred to as neck-bondedlaminates, are formed by bonding the necked nonwoven web to the elasticfilm or nonwoven web when the former is in the neck-stretched state.

Neck-bonded laminates are described in numerous patents to Morman et al.Representative patents include without limitation U.S. Pat. Nos.5,226,992; 5,336,545; 5,514,470; 5,910,224 and 6,475,600, which areincorporated by reference.

While neck-bonded laminates provide suitable cross-direction elasticityfor a wide variety of applications, they typically involve use of astructurally integrated elastic nonwoven web or film (i.e. a layer whichis elastic in all directions) to provide elasticity to the laminate,even when elasticity is required in only one direction, such as thecross-direction of the laminate. A full coverage layer of elastic web orfilm has disadvantages when used to produce a laminate that is elasticin only one direction, such as the cross direction. First, the amount ofelastic polymer used may be more than what is required for thecross-direction elastic laminate since the requirement to form the webor film will dictate the minimum basis weight of the elastic material.Second, an elastic film may limit the laminate to a low amount of watervapor transmission (breathability). Third, elastic webs or films (morethan individual filaments) are influenced by the physics of Poisson'sratio which retracts the web or film perpendicular to the direction ofstretch. Fourth, webs or films which stretch in both directions requirespecial processing techniques in converting machines because a machinedirection stretch causes control problems in tension-controlled sectionsof the machines. For applications where elasticity is only needed in thecross-direction, there is a need or desire for a neck-bonded laminatewhich limits the amount of elastic material to that needed to obtain theunidirectional elasticity, and a method for making such a laminate.

SUMMARY OF THE INVENTION

The present invention is directed to a cross-directional elasticizedcomposite material, and a method of making it. The composite materialincludes at least one facing material, which can be a nonwoven webhaving a machine direction (which is a direction of manufacture of thenonwoven web) and a cross-direction (which is perpendicular to thedirection of manufacture). The facing layer can be a necked nonwovenweb, which has been neck-stretched in the machine direction to causenarrowing (necking) in the cross direction. The nonwoven web can beformed of inelastic filaments.

The composite material also includes elastic filaments which aredisposed in the cross-direction of the facing layer, or significantly inthe cross direction (i.e. within about 45 degrees of the crossdirection) of the facing layer. The elastic filaments can besubstantially parallel to each other, and can be spaced apart andnon-intersecting with respect to each other. The elastic filaments aresuitably bonded to the facing layer.

The elastic composite material can be prepared by a method whichincludes the steps of:

feeding a facing layer to a first mandrel at an angle relative to alongitudinal axis of the first mandrel;

rotating the first mandrel in a first direction around the axis, whileconveying the facing layer axially forward, causing the facing layer towrap around the first mandrel in a spiral fashion;

conveying the facing material between an extrusion die and an innersurface of a second mandrel;

rotating the extrusion die in a second direction opposite the firstdirection while simultaneously extruding elastic polymer filaments fromthe extrusion die onto the facing layer, to form a laminate; and

severing the elastic filaments along edges of the laminate to form theelastic composite material.

The elastic polymer filaments are suitably bonded to the facing materialby melt bonding immediately following their extrusion, without requiringa separate adhesive material.

With the foregoing in mind, it is a feature and advantage of theinvention to provide an improved, lower cost cross-direction elasticizedcomposite material, and a method of making it.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 schematically illustrates an elastic composite material of theinvention and an apparatus and method for making it.

FIG. 2 is a partial sectional view at the apparatus shown in FIG. 1,illustrating the rotating die and the joining of extruded elasticfilaments to the facing layer.

FIG. 3 is a perspective view of a second end of the apparatus shown inFIG. 1, with the rotating die removed.

FIG. 4 is a sectional view of a first end of the apparatus shown in FIG.1, emphasizing a gear box assembly.

DEFINITIONS

“Bonded” and “bonding” refer to the joining, adhering, connecting,attaching, or the like, of two elements. Two elements will be consideredto be bonded together when they are bonded directly to one another orindirectly to one another, such as when each is directly bonded tointermediate elements.

“Melt bonding” refers to mechanical and/or chemical bonding of elasticfilaments to a facing material via contact and/or penetration of themolten filament polymer into the surface of the facing material,resulting in bonding without the use of separate adhesive materials(i.e. separate from inherent adhesive properties of the molten filamentpolymer and additives compounded into the polymer).

“Breathable film” or “breathable laminate” refers to a film or laminatehaving a water vapor transmission rate (“WVTR”) of at least about 500grams/m²-24 hours, using the WVTR Test Procedure described herein.

“Elastomeric” or “elastic” refers to a material or a composite which canbe elongated by at least 50 percent of its relaxed length in at leastone direction and which will recover, upon release of the applied force,at least 40 percent of its elongation. An elastomeric material orcomposite may be capable of being elongated by at least 100 percent, orby at least 300 percent, of its relaxed length and recover, upon releaseof an applied force, at least 50 percent of its elongation, orsubstantially all of its elongation. An “elasticized” material orcomposite is one which has been rendered elastic, such as by affixingelastic strands to an inelastic facing layer.

“Inelastic” refers to materials that are not elastic, either becausethey cannot be sufficiently stretched, or because they do notsufficiently recover when a stretching force is removed.

“Machine direction” as applied to a facing layer, refers to thedirection on the material that was parallel to the direction of travelof the material as it left the extrusion or forming apparatus. If thematerial passed between nip rollers or chill rollers, for instance, themachine direction is the direction on the material that was parallel tothe surface movement of the rollers when in contact with the material.“Cross direction” refers to the direction perpendicular to the machinedirection. Dimensions measured in the cross direction are referred to as“width” dimensions, while dimensions measured in the machine directionare referred to as “length” dimensions. As used herein, “machinedirection” and “cross direction” of a laminate or composite refer to the“machine direction” and “cross direction,” respectively, of a facinglayer in the laminate.

“Meltblown fibers” are fibers formed by extruding a molten thermoplasticmaterial through a plurality of fine, usually circular, die capillariesas molten threads or filaments into converging high velocity heated gas(e.g., air) streams which attenuate the filaments of moltenthermoplastic material to reduce their diameter, which may be tomicrofiber diameter. Thereafter, the meltblown fibers are carried by thehigh velocity gas stream and are deposited on a collecting surface toform a web of randomly dispersed meltblown fibers. Such a process isdisclosed for example, in U.S. Pat. No. 3,849,241 to Butin et al.Meltblown fibers are microfibers which may be continuous ordiscontinuous, are generally smaller than about 1.0 denier, and aregenerally self bonding when deposited onto a collecting surface.

“Neck” or “neck stretch” interchangeably mean that the fabric, nonwovenweb or laminate is stretched in its machine direction under conditionsreducing its width or its transverse dimension and increasing itslength. The controlled stretching may take place at room temperature orgreater temperatures and is limited to an increase in overall length inthe direction being stretched up to the elongation required to break thefabric, nonwoven web or laminate, which in most cases is about 1.1 to1.6 times an original length, suitably about 1.2 to 1.5 times anoriginal length. When relaxed, the fabric, nonwoven web or laminate doesnot return to its original dimensions unless it is then stretched in thecross direction. The necking process typically involves unwinding asheet from a supply roll and passing it through a first nip rollassembly driven at a given linear speed. A second nip roll assembly,operating at a linear speed higher than the first nip roll assemblygenerates the tension needed to elongate and neck the fabric. U.S. Pat.No. 4,965,122 issued to Morman, and commonly assigned to the assignee ofthe present invention, discloses a reversibly necked nonwoven materialwhich may be formed by necking the material, then heating the neckedmaterial, followed by cooling and is incorporated by reference. Theheating of the necked material causes additional crystallization of thepolymer giving it a partial heat set. If the necked material is aspunbond web, some of the fibers in the web may become crimped duringthe necking process, as explained in U.S. Pat. No. 4,965,122.

As used herein, the term “necked material” refers to any material whichhas been drawn in at least one dimension, (e.g. lengthwise), reducingthe transverse dimension, (e.g. width), such that when the drawing forceis removed, the material can be pulled in the cross direction back toits original width. The necked material generally has a higher basisweight per unit area than the pre-necked material. When the neckedmaterial is pulled back to its original width, it should have about thesame basis weight as the pre-necked material. Materials suitable fornecking include without limitation nonwoven webs formed from inelasticpolymers.

“Neck-bonded laminate” refers to a laminate formed while a first layer,typically a nonwoven fabric, is in a necked condition. A second layer(e.g. an elastic layer) is bonded to the necked layer, and may berelaxed when the laminate is formed.

“Nonwoven” or “nonwoven web” refers to materials and webs of materialhaving a structure of individual fibers or filaments which areinterlaid, but not in an identifiable manner as in a knitted fabric.Nonwoven fabrics or webs have been formed from many processes such as,for example, meltblowing processes, spunbonding processes, air layingprocesses, coforming processes, and bonded carded web processes. Thebasis weight of nonwoven fabrics is usually expressed in ounces ofmaterial per square yard (osy) or grams per square meter (gsm) and thefiber diameters are usually expressed in microns. (Note that to convertfrom osy to gsm, multiply osy by 33.91.)

“Polymers” include, but are not limited to, homopolymers, copolymers,such as for example, block, graft, random and alternating copolymers,terpolymers, etc. and blends and modifications thereof. Furthermore,unless otherwise specifically limited, the term “polymer” shall includeall possible geometrical configurations of the material. Theseconfigurations include, but are not limited to isotactic, syndiotacticand atactic symmetries.

“Retract” and “retractability” refer to a material's ability to recovera certain amount of its elongation upon release of an applied force.

“Spunbond fiber” refers to small diameter fibers which are formed byextruding molten thermoplastic material as filaments from a plurality offine capillaries of a spinnerette having a circular or otherconfiguration, with the diameter of the extruded filaments then beingrapidly reduced as by, for example, in U.S. Pat. No. 4,340,563 to Appelet al., and U.S. Pat. No. 3,692,618 to Dorschner et al., U.S. Pat. No.3,802,817 to Matsuki et al., U.S. Pat. Nos. 3,338,992 and 3,341,394 toKinney, U.S. Pat. No. 3,502,763 to Hartmann, U.S. Pat. No. 3,502,538 toPetersen, and U.S. Pat. No. 3,542,615 to Dobo et al., each of which isincorporated by reference. Spunbond fibers are quenched and generallynot tacky when they are deposited onto a collecting surface. Spunbondfibers are generally continuous and often have average deniers largerthan about 0.3, more particularly, between about 0.6 and 10. These andother terms may be defined with additional language in the remainingportions of the specification.

DETAILED DESCRIPTION OF THE INVENTION

Referring to FIG. 1, an elasticized composite material 10, which can bea neck-bonded laminate, includes a facing layer 12 having a machinedirection indicated by arrow 11 and a cross direction perpendicular tothe machine direction indicated by arrow 13. A plurality of elasticfilaments 14 are bonded to the facing layer 12 and disposed in the crossdirection.

The facing layer 12 may be a necked nonwoven web which has beenstretched in the machine direction 11 to narrow (neck) its width in thecross direction 13. When the necked nonwoven web is later stretched inthe cross direction, it may extend at least back to its original(pre-necked) width. Suitable necked nonwoven webs may be formed fromspunbond webs, meltblown webs, bonded carded webs, other webs wherethere has been at least some bonding between the fibers, andcombinations thereof. The nonwoven webs used for necking are typicallyformed of inelastic polymers, including without limitation polyethylene,polypropylene, copolymers of ethylene or propylene with up to 10% byweight of an olefin comonomer, polyesters, polyamides and the like.

The facing layer 12 may also be a material that is inherently extensiblein the cross direction 13 but does not independently possess sufficientretractive force to constitute an elastic material. Such materials neednot be necked. Bonded carded webs, for instance, possess some inherentextensibility in the cross direction. Other inherently extensiblematerials include films and nonwoven webs formed from inherentlyextensible polymers, including without limitation single-site catalyzedethylene-alpha olefin copolymers having relatively high (e.g. more than10% by weight) comonomer contents, and blends thereof.

The elastic filaments 14 may be joined to the facing layer 12, and aresuitably joined by melt-bonding which occurs when the elastic filaments14 are deposited in a molten state on the facing layer 12. Themelt-bonding may be a final bonding step, suitable for end use of thelaminate, or an interim bonding step adequate to progress the elasticfilaments and facing layer without distortion to a subsequent bondingstation where the filaments and facing may be further bonded using aspray adhesive, slot adhesive, ultrasonic bonding, thermal bonding orthe like. The elastic filaments 14 are disposed on the facing layer 12significantly in the cross direction. This means that the elasticfilaments 14 may be disposed precisely in the cross direction 11, or maybe disposed at an angle of about −30 degrees to about +30 degreesrelative to the cross direction 13. Suitably, the elastic filaments maybe disposed between about −15 degrees and about +15 degrees relative tothe cross direction 13, or between about −5 and about +5 degreesrelative to the cross direction 13.

The elastic filaments 14 can be formed of elastic polymers, and blendscontaining sufficient amounts of elastic polymer to render the filamentselastic. Suitable elastic polymers include without limitation styrenicblock copolymers, for example styrene-diene and styrene-olefin blockcopolymers sold under the trade name KRATON® by Kraton Polymers, LLC.

Suitable styrene-diene block copolymers include di-block, tri-block,tetra-block and other block copolymers, and may include withoutlimitation styrene-isoprene, styrene-butadiene,styrene-isoprene-styrene, styrene-butadiene-styrene,styrene-isoprene-styrene-isoprene, andstyrene-butadiene-styrene-butadiene block copolymers. Suitablestyrene-olefin block polymers include without limitation styrene-dieneblock copolymers in which the diene groups have been totally orpartially selectively hydrogenated, including without limitationstyrene-(ethylene-propylene), styrene-(ethylene-butylene),styrene-(ethylene-propylene)-styrene,styrene-(ethylene-butylene)-styrene,styrene-(ethylene-propylene)-styrene-(ethylene-propylene), andstyrene-(ethylene-butylene)-styrene-(ethylene-butylene) blockcopolymers. In the above formulas, the term “styrene” indicates a blocksequence of styrene repeating units; the terms “isoprene” and“butadiene” indicate block sequences of diene units; the term“(ethylene-propylene)” indicates a block sequence of ethylene-propylenecopolymer units, and the term “(ethylene-butylene)” indicates a blocksequence of ethylene-butylene copolymer units. The styrene-diene orstyrene-olefin block copolymer should have a styrene content of about 10to about 50% by weight, suitably about 15 to about 25% by weight, andshould have a number average molecular weight of at least about 40,000grams/mol, suitably about 60,000 to about 110,000 grams/mol.

Other suitable elastic polymers include without limitation single-sitecatalyzed ethylene-alpha olefin copolymer resins having a density ofabout 0.915 grams/cm³ or less, suitably about 0.860-0.900 grams/cm³,particularly about 0.865-0.895 grams/cm³. The term “single-sitecatalyzed” includes without limitation ethylene-alpha olefin copolymersformed using metallocene or constrained geometry catalysts. Examples ofsingle-site catalysts include bis(n-butylcyclopentadienyl)titaniumdichloride, bis(n-butylcyclopentadienyl)zirconium dichloride,bis(cyclopentadienyl)scandium chloride, bis(indenyl)zirconiumdichloride, bis(methylcyclopentadienyl)titanium dichloride,bis(methylcyclopentadienyl)zirconium dichloride, cobaltocene,cyclopentadienyltitanium trichloride, ferrocene, hafnocene dichloride,isopropyl(cyclopentadienyl,-1-flourenyl)zirconium dichloride,molybdocene dichloride, nickelocene, niobocene dichloride, ruthenocene,titanocene dichloride, zirconocene chloride hydride, zirconocenedichloride, among others. A more exhaustive list of such compounds isincluded in U.S. Pat. No. 5,374,696 to Rosen et al. and assigned to theDow Chemical Company. Such compounds are also discussed in U.S. Pat. No.5,064,802 to Stevens et al. and also assigned to Dow. However, numerousother single-site catalyst systems are known in the art; see forexample, U.S. Pat. No. 5,539,124 to Etherton et al.; U.S. Pat. No.5,554,775 to Krishnamurti et al.; U.S. Pat. No. 5,451,450 to Erderly etal. and The Encyclopedia of Chemical Technology, Kirk-Othemer, FourthEdition, vol. 17, Olefinic Polymers, pp. 765-767 (John Wiley & Sons1996); the entire contents of the aforesaid patents being incorporatedherein by reference.

The single-site catalyzed ethylene-alpha olefin copolymer may be formedusing a C₃ to C₁₂ alpha-olefin comonomer, and is suitably formed using abutene, hexene or octene comonomer. The amount of the comonomer isnormally between about 5-25% by weight of the copolymer, and may varydepending on how much comonomer is needed to achieve the desireddensity. Normally, higher comonomer amounts and/or larger comonomermolecules result in lower densities. The low performance elastomer mayhave a number average molecular weight of at least about 30,000grams/mol, suitably about 50,000 to about 110,000 grams/mol, and mayhave a melt index of about 0.5-30 grams/10 min. at 190° C., suitablyabout 2-15 grams/10 min, measured using ASTM D-1238, Condition E.Suitable single-site catalyzed ethylene-alpha olefin copolymers are madeand sold by the Dow Chemical Company under the trade names AFFINITY andENGAGE, and by the ExxonMobil Chemical Co. under the trade names EXACTand EXCEED.

The elastic filaments 14 impart cross-directional elasticity to thecomposite laminate 10. The facing layer 12 can be stretched in the crossdirection, but need not have independent retractive force. As shown inFIG. 1, the elastic filaments 14 terminate at the longitudinal sideedges 16 and 18 of the laminate 10, which correspond to longitudinalside edges of the facing layer 12. The elastic filaments 14 are suitablyspaced apart and nonintersecting relative to each other, and aresuitably parallel or substantially parallel to each other.

The diameter and spacing of elastic filaments 14 may vary depending onthe type of elastic polymer, the end use application(s) for thecomposite laminate 10, the amount of retractive force desired, and otherfactors. For example, elastic filaments 14 may have individual diametersof about 50 microns to about 5 mm, suitably about 100 microns to about 1mm, and may have uniform or nonuniform diameters. The elastic filaments14 may be spaced apart by distances of about 1 mm to about 25 mm,suitably about 3 mm to about 12 mm, and may be uniformly or nonuniformlyspaced. The elastic filaments 14 may cover about 5% to about 75% of asurface area of the facing layer 12, suitably about 10% to about 50%.

The facing layer 12 should have a cross-directional extensibility whichis sufficient to permit the laminate 10 to behave as an elasticcomposite material. The facing layer 12 may have a cross-directionalextensibility of at least about 50%, suitably at least about 100%, or atleast about 200%, or at least about 300%. When the facing layer 12 is anecked nonwoven web, the cross-directional extensibility may be achievedby neck-stretching the precursor nonwoven web to about 1.1-1.6 times itsinitial length in the machine direction, suitably to about 1.2-1.5 timesits initial length.

The composite elastic laminate 10 may include a second facing layer (notshown) which is subsequently applied over the elastic filaments 14 afterthey are bonded to the first facing layer 12. The second facing layermay be formed of the same or different materials as the first facinglayer 12, and should be extensible in the cross direction to the same ora similar extent as the first facing layer 12. The second facing layermay be applied using known techniques of thermal calendar bonding,adhesive bonding, ultrasonic bonding or the like.

Referring to FIGS. 1 and 2, a method and apparatus 50 are shown formaking an elastic composite material, such as the composite elasticlaminate 10 described above. A facing layer 12, which can be a spunbondweb or other nonwoven fabric, is unwound from an unwinder 52 and passedthrough a necking process 54 to form a necked nonwoven web, forinstance. The unwinder 52 and necking process 54 are conventionalprocess elements and are illustrated in block form, with detailsomitted.

The facing layer 12 is fed to a first mandrel 56, with the machinedirection 11 of facing layer 12 approaching first mandrel 56 at an anglerelative to its longitudinal axis 57. The angle between the machinedirection 11 of facing layer 12 and longitudinal axis 57 of firstmandrel 56 can be about 15-75 degrees, suitably about 30-60 degrees, orabout 40-50 degrees. The first mandrel is rotated in a first direction58, while simultaneously conveying the facing layer 12 forward in anaxial direction 59, causing the facing layer 12 to wrap around firstmandrel 56 in a spiral fashion.

As further illustrated in FIGS. 1-4, the facing layer 12 may be axiallymoved along the first mandrel 56 using a plurality of conveyor belts 60driven by pulleys 62 and 64, which are synchronized for axial motion ata speed relative to the rotational surface velocity of the first mandrel56. If the facing layer 12 approaches the first mandrel 56 at a45-degree angle relative to the axis 57, then the axial velocity of theconveyor belts 60 should equal the rotational surface velocity of firstmandrel 56. If the facing layer 12 approaches the first mandrel 56 at anangle less than 45 degrees, then the axial velocity of conveyor belts 60should exceed the rotational surface velocity of first mandrel 56. Forinstance, a 30-degree approaching angle would require the axial velocityto be twice the rotational surface velocity. If the facing layer 12approaches the first mandrel 56 at an angle greater than 45 degrees,then the rotational surface velocity of first mandrel 56 should exceedthe axial velocity of conveyor belts 60.

The size and number of conveyor belts 60 around the circumference of thefirst mandrel 56 should be sufficient to control the forward axialmovement of facing layer 12. If the inner mandrel 56 has a diameter ofabout 10-20 inches, for instance, the number of conveyor belts 60 mayrange from about 4-30, suitably about 6-24, or about 8-20. Each conveyorbelt 60 is positioned with its outward facing portion 66 about even withan outer surface of first mandrel 56, and with its inward facing portion68 extending through an interior of first mandrel 56.

The axial motion of conveyors 60 and rotational motion of first mandrel56 can be synchronized using a crossed helical gear assembly 70 (FIG. 4)mounted on drive shaft 72 at the first end 74 of mandrel 56. The gearassembly 70 includes outer gears 78 which engage a large diameter,non-rotating internal helical gear 80 which can be mounted to the floor.The teeth of gear 80 are crossed to those of mating outer helical gears78. The outer helical gears 78 mesh with inner helical gears 82 innon-crossed fashion. Pulleys 62 are made an integral part of gears 82 bycutting a deep grove 81 at or near the centers of the gear faces. Thediameters of all three sets of gears 78, 80 and 82 and the diameter ofthe groves 81 forming the pulleys 62 are designed to provide the correctrelation between the axial velocity of conveyor belts 60 and therotational surface velocity of inner mandrel 56. As explained above, theaxial speed of conveyor belts 60 and the surface speed of mandrel 56will be designed to be equal in the case of a 45-degree approach offacing layer 12 to mandrel 56.

As best illustrated in FIG. 2, the facing layer 12 is conveyed forwardin a spiral path beyond a terminal end 84 of the first mandrel 56, andbetween an extrusion die 86 and an inner surface 88 of a second mandrel90. The second mandrel 90 is concentric with the first mandrel 56,encloses a portion of the first mandrel 56 (FIGS. 1 and 3), and extendsbeyond terminal end 84 of first mandrel 56. The second mandrel 90 isstationary, and does not rotate.

The extrusion die 86 includes a row of circumferentially spaced dieopenings 92 extending completely around its outer circumference 94. Theextrusion die 86 is caused to rotate in a direction 96 (opposite thedirection of rotation 58 of first mandrel 56) at an approximate speedrelative to facing layer 12 and mandrel 56 so as to deposit filaments indirection 13 or substantially in that direction. At commercialmanufacturing speeds the centrifugal force of polymer leaving dieopenings 92 is sufficient to cause a uniform, evenly spaced depositionof molten elastic filaments 14 on a surface of facing layer 12. Thecentrifugal force exerted on molten elastic filaments 14 by the rotationof extrusion die 86 is greater than gravitational force G, suitablygreater than 2G, or about 4G to about 10G. By applying a reasonablemultiple of gravitational force via rotation of die 86, the elasticfilaments 14 can be applied substantially uniformly regardless ofwhether the filaments 14 are extruded near the top of the rotation(against the force of gravity) or near the bottom of the rotation (withassistance from gravity). However, if the rotation achieves acentrifugal force that is too high, the elastic filaments 14 may breakfollowing extrusion before they contact the facing layer 12.

First mandrel 56 is cantilevered from its first end and, withoutadditional support, would be unstable at its second end while rotatingat commercial speeds. Extrusion die 86 is therefore configured withsupport extension 120 so that when the die 86 is slid into operatingposition the support extension 120 (having tapered end 121) is acceptedinto opening 130 and pilot bearing 140 at the second end of mandrel 56,to provide sufficient support.

The process conditions (melt temperature, extruder rpm, etc.) aresuitably adjusted so that the molten elastic filaments 14 “melt bond”(adhere) to the facing layer 12 without the aid of an adhesive.Alternatively, the facing layer 12 may be treated with an adhesive toassist in the bonding.

The optimum centrifugal force exerted by rotation of die 86 will dependpartly on the elastomeric polymer type, molecular weight and viscosity,the extrusion temperatures, the size of die openings 92 and otherprocess factors. To minimize breakage of molten elastic filaments 14, itis also desirable to maintain a relatively small spacing 98 between thedie openings 92 and the facing layer 12, as shown in FIG. 2. The spacing98 can be on the order of about 3 mm to about 30 mm, suitably about 5 mmto about 15 mm.

As illustrated in FIG. 2, the second mandrel 90 extends beyond theterminal end 84 of the first mandrel 56 and surrounds at least theportion of rotating die 86 that includes die openings 92. After thefacing layer 12 is conveyed between the inner surface 88 of the secondmandrel 90 and the openings 92 of the rotating die, the resultinglaminate 10 is conveyed around a terminal end 99 of the second mandrel90 and to an outer surface 101 of the second mandrel 90. A slittingmechanism 103 (FIG. 1), such as a blade or knife assembly, can bemounted with respect to the outer surface 101 near the terminal end 99to sever the elastic filaments 14 along longitudinal side edges 16 and18 of the composite elastic laminate 10 and facing layer 12.

Because the first mandrel 56 is rotating in the first direction whileconveying the facing layer 12 axially, the facing layer maintains theresulting spiral path throughout the deposition of elastic filaments 14onto facing layer 12. The rotation of the extrusion die in the second,opposite direction, expressed by N₀, as revolutions per minute, can beadjusted to extrude the elastic filaments 14 onto the facing layer 12 ata desired angle. In order to achieve a significantly cross-directionaldisposition of elastic filaments 14, they should be extruded onto thefacing layer at an angle of about −30 degrees to about +30 degrees, orabout −15 degrees to about +15 degrees, or about −5 degrees to about +5degrees, relative to the cross direction of the facing layer.

In many instances, it may be desirable to achieve a perfect ornear-perfect cross-directional disposition of elastic filaments 14 ontothe facing layer 12. Referring to FIG. 1, if the facing layer 12 isconveyed in the machine direction 11 at a velocity V, and if itapproaches the first mandrel 56 at an angle of 45 degrees, the angularvelocity N₀ of the rotating die 86 required to achieve cross-directionaldisposition of elastic filaments 14 can be calculated from the followingequation: $N_{0} = \frac{V\sqrt{2}}{\Pi\quad D_{0}}$

where N₀ is the rpm of the extrusion die,

-   -   V is the machine direction velocity of the facing layer, and    -   D₀ is the outer diameter of the first (rotating) mandrel.

Similarly, the linear (axial) speed of the conveyor belts 60 required toconvey the facing layer can be designated as V_(b) and determined fromthe following equation: $V_{b} = \frac{V}{\sqrt{2}}$

In the embodiment shown in FIG. 2, the openings 92 in rotating die 86are configured to provide elastic filaments which are spaced apart,nonintersecting and substantially parallel to each other, with uniformsize and spacing between filaments. It is also possible to provideopenings 92 of larger and smaller size, and/or greater and lesserspacing, to create zones of higher and lower elastic tension on thecomposite elastic laminate 10. The die openings 92 may also be arrangedin more than one row.

It is desired to minimize friction between the facing layer 12 and thesecond mandrel 90, especially when the composite laminate 10 is conveyedfrom the inner surface 88, around the terminal edge 99, to the outersurface 101 of the second mandrel 90. As illustrated in FIGS. 1 and 3,this friction can be minimized by equipping the terminal end 99 andouter surface 101 of mandrel 90 with a plurality of rollers 105 and 110,suitably mounted in openings 107 in the mandrel and slots 109 in theterminal end 99.

The minimization of friction is especially important due to variationsin the length of contact between the second mandrel 90 and the laminate10 across its lateral width. As illustrated in FIG. 1, the first edge 16of the laminate 10 is caused to leave the second mandrel after theelastic filaments 14 are severed, immediately after the first edge 16 isdrawn around the terminal edge 99 of the second mandrel 90. However, thesecond edge 18 of the laminate 10 is caused to leave (i.e. depart fromthe outer surface 101 of) the second mandrel 90 after traversing thesecond mandrel with one spiral wrap after being drawn around theterminal edge 99 of the second mandrel 90. By minimizing the frictionbetween the laminate 10 and the second mandrel 90, the effects on thelaminate 10 resulting from the varying length of contact are minimized.

In another variation, the entire apparatus 50 (FIG. 1) may be mountedvertically instead of horizontally as shown, to facilitate more evendisposition of elastic filaments 14 and eliminate nonuniformities causedby gravity.

The embodiments of the invention described herein are exemplary. Variousmodifications and improvements can be made without departing from thespirit and scope of the invention. The scope of the invention isindicated by the appended claims, and all equivalents are intended to beencompassed within their scope.

1. A neck-bonded laminate, comprising: a necked nonwoven webneck-stretched in a machine direction to cause narrowing in a crossdirection perpendicular to the machine direction; and a plurality ofelastic filaments joined to the necked nonwoven web and disposedsignificantly in the cross direction.
 2. The neck-bonded laminate ofclaim 1, wherein the elastic filaments are directly bonded to the neckednonwoven web by melt bonding.
 3. The neck-bonded laminate of claim 1,wherein the elastic filaments are spaced apart and nonintersecting withrespect to each other.
 4. The neck-bonded laminate of claim 1, whereinthe elastic filaments are substantially parallel to each other.
 5. Theneck-bonded laminate of claim 1, wherein the elastic filaments aredisposed between about −30 degrees and about +30 degrees relative to thecross direction.
 6. The neck-bonded laminate of claim 1, wherein theelastic filaments are disposed between about −15 degrees and about +15degrees relative to the cross direction.
 7. The neck-bonded laminate ofclaim 1, wherein the elastic filaments are disposed between about −5degrees and about +5 degrees relative to the cross direction.
 8. Theneck-bonded laminate of claim 1, wherein the necked nonwoven web isstretched to about 1.1 to about 1.6 times an initial length in themachine direction.
 9. The neck-bonded laminate of claim 1, wherein thenecked nonwoven web is stretched to about 1.2 to about 1.5 times aninitial length in the machine direction.
 10. The neck-bonded laminate ofclaim 1, wherein the necked nonwoven web comprises a fibrous webselected from the group consisting of spunbond webs, meltblown webs,bonded carded webs, and combinations thereof.
 11. The neck-bondedlaminate of claim 1, wherein the elastic filaments terminate atlongitudinal side edges of the necked nonwoven web.
 12. A method ofmaking an elastic composite material, comprising the steps of: feeding afacing layer to a first mandrel at an angle of about 15 to about 75degrees relative to a longitudinal axis of the first mandrel; rotatingthe first mandrel in a first direction around the axis, while conveyingthe facing layer axially forward, causing the facing layer to wraparound the first mandrel in a spiral fashion; conveying the facingmaterial beyond a terminal end of the first mandrel, and between anextrusion die and an inner surface of a second mandrel; rotating theextrusion die in a second direction opposite the first direction whilesimultaneously extruding elastic polymer filaments from the extrusiondie onto the facing layer, to form a laminate; and severing the elasticfilaments along longitudinal side edges of the facing layer to form theelastic composite material.
 13. The method of claim 12, wherein thefacing layer is fed to the first mandrel at an angle of about 30 toabout 60 degrees relative to the axis.
 14. The method of claim 12,wherein the facing layer is fed to the first mandrel at an angle ofabout 40 to about 50 degrees relative to the axis.
 15. The method ofclaim 12, wherein the elastic polymer filaments are extruded onto thefacing layer at an angle between about −30 degrees and about +30 degreesrelative to a cross direction of the facing layer.
 16. The method ofclaim 15, wherein the elastic polymer filaments are extruded onto thefacing layer at an angle of about −15 degrees to about +15 degreesrelative to the cross direction.
 17. The method of claim 15, wherein theelastic polymer filaments are extruded onto the facing layer at an angleof about −5 degrees to about +5 degrees relative to the cross direction.18. The method of claim 12, further comprising the step of melt bondingthe elastic polymer filaments to the facing layer.
 19. The method ofclaim 12, further comprising the step of passing the laminate around aterminal edge of the second mandrel to an outer surface of the secondmandrel before severing the elastic filaments.
 20. The method of claim12, wherein the facing layer comprises a necked nonwoven web.
 21. Themethod of claim 12, wherein the elastic filaments are spaced apart andnonintersecting relative to each other.
 22. The method of claim 12,wherein the first mandrel comprises a plurality of axially disposedconveyor belts for conveying the facing material axially forward. 23.The method of claim 19, further comprising the steps, after severing theelastic filaments, of: a) causing a first edge of the laminate to leavethe second mandrel immediately after being drawn around the terminaledge of the second mandrel; and b) causing a second edge of the laminateto leave the second mandrel after traversing the second mandrel with onespiral wrap after being drawn around the terminal edge of the secondmandrel.
 24. A method of making an elastic composite material,comprising the steps of: feeding a facing layer to an outer surface of afirst cylindrical mandrel at an angle relative to a longitudinal axis ofthe mandrel; rotating the first mandrel in a first direction around theaxis, while conveying the facing layer axially forward, causing thefacing layer to wrap around the mandrel in a spiral fashion; conveyingthe facing material between an extrusion die and an inner surface of asecond cylindrical mandrel that is concentric with the first cylindricalmandrel; rotating the extrusion die in a second direction opposite thefirst direction while simultaneously extruding spaced-apart elasticfilaments from the extrusion die onto the facing layer, to form alaminate; and severing the elastic filaments along edges of the laminateto form the elastic composite material.
 25. The method of claim 24,wherein the facing layer is fed to the outer surface of the firstcylindrical mandrel at a linear velocity V, the first cylindricalmandrel has an outer diameter D₀, and the extrusion die is rotated at aspeed N₀, in revolutions per minute, defined by the equation:$N_{0} = \frac{V\sqrt{2}}{\Pi\quad D_{0}}$
 26. The method of claim 24,wherein the first cylindrical mandrel comprises a plurality of axiallydisposed conveyor belts for conveying the facing material forward. 27.The method of claim 26, wherein the facing layer is fed to the outersurface of the first cylindrical mandrel at a linear velocity V, and theaxially disposed conveyor belts move along the axis at a speed V_(b)defined by the equation: $V_{b} = \frac{V}{\sqrt{2}}$
 28. The method ofclaim 24, wherein the first cylindrical mandrel is disposed partiallywithin the second cylindrical mandrel.
 29. The method of claim 24,further comprising the step of passing the laminate around a terminaledge of the second cylindrical mandrel to an outer surface of the secondcylindrical mandrel before severing the elastic filaments.